DEV Community

Piping JavaScript

K on February 04, 2018

Cover image by arbyreed on Flickr. JavaScript is getting more and more functional programming features, an exiting one is the new pipeline operato...

Read full post

𝔞𝔞𝔯𝔬𝔫 🅥 • Feb 4 '18

As an avid Elixir user this couldn’t make me happier!

Alex Casalboni • Feb 8 '18

Coming from the "old world", it looks a bit weird at first :)

Looking at |> addDays(2), I would expect addDays(2) to be evaluated before being used as a function. In my mind, this can only work if addDays(2) actually returns a function.

K • Feb 9 '18 • Edited

> In my mind, this can only work if addDays(2) actually returns a function.

This is what it does :)

A regular version of that function would look like that:

function addDays(amount, date) {...}

addDays(2, date);

A curried version looks like that:

const addDays = amount => date => {...};

addDays(2)(date);

Roman Kuba • Feb 4 '18

As I didn't come around to try this yet, I have one question.
Does the pipe operator know where to put the output of the previous function as input on the next one?
I am asking because:

const add2Days = addDays(2);

Takes the value as the second param.

const customFormat = format("D MMMM YYYY");

though takes the value as the first param.

Overall I think it's awesome that this comes to JS.
And a thank you for the posts you are putting out. Always looking forward to them.

K • Feb 4 '18 • Edited

I think I wrote it wrong. It always uses the first argument. fixed it.

JasonSooter • Feb 4 '18 • Edited

I enjoy the pipe function in RamdaJS. It's gonna be nice to have this natively.

Cristian Pallarés • Feb 5 '18

I guess it's the same as the flow function in Lodash, isn't it? I always use it!

K • Feb 4 '18

RamdaJS is pretty awesome, yes.

Vedran Mandić • Mar 11 '19

I love it, and truly believe this is one small (big) step to popularize FP. Can be retrofitted with a pipe() fn (hint RamdaJS) for those who dislike the operator (for now!). Cool summary.